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16 Dental Tribune United Kingdom Edition | 1/2017 TRENDS & APPLICATIONS “Essentially, we are not adapted to the diets we eat today” An interview with Prof. Debbie Guatelli-Steinberg, US By Kristin Hübner, DTI In her book What Teeth Re- veal About Human Evolution (Cambridge University Press, 2016), anthropologist Prof. Debbie Guatelli-Steinberg describes what fossilised teeth reveal about history and the living conditions of our ancestors. One finding is that the high proportion of soft and sugary food people consume in the Western world these days is to blame for the steady rise of dental problems such as dental de- cay and malocclusion. Dental Tribune had the opportunity to speak to the Ohio State University professor about the causes of this develop- ment and the impact her re- search may have on modern life. Dental Tribune: Prof. Guatelli-Stein- berg, you are studying fossilised teeth in order to shed light on the living conditions of our ancestors. What can teeth reveal about earlier life and human evolution? Prof. Guatelli-Steinberg: Teeth make up most of the mammalian fossil record, and this is true for human evolution as well. The rea- son:teethareheavilymineralised, so they resist destruction and de- composition. The fact that teeth are likely to fossilise is extremely convenient for physical anthro- pologists because teeth lock de- tailed information about diet and growth into their physical and chemical structure. The book is meant to synthesise insights into human evolution that researchers have gleaned from teeth—those insights include the recognition that human diets began to diver- sify early in hominin evolution, making it possible for our lineage to ride out fluctuations in food availability. From daily growth lines in teeth, researchers have been able to calculate the length of time teeth took to develop and erupt into the oral cavity. And, since dental development is linked to the development of the organism as a whole, it has been possible to use the pace of dental growth and development to gauge the evolution of the protracted child- hoods that are a unique feature of humans among other primates. It is even possible, and much of my own research is about this, to use growth lines in teeth to assess the timing and duration of enamel growth disruption, pro- viding insight into periods of physiological stress (malnutrition, illness) in the individual lives of our ancestors. What sparked your interest in this field of research initially? I have always had an interest in human evolution and non-human primates, and when I began my doctoral program at the Univer- sity of Oregon, I met Prof. John Lukacs, who used teeth to answer questions related to these topics. This seemed like a really fascinat- ing thing to me—that one could find out so much from fossil teeth. How does one decode the informa- tiongarneredfromfossilisedteeth? One can gain information about growth rates and develop- ment in teeth or about the morphology of teeth, but that information requires a broader context for inter- pretation. For example, human first molars erupt at around six years of age, but that fact does not tell one much unless one com- pares it with other mam- mals, especially non-hu- man primates. Dogs grow up fast and their first permanent teeth erupt around six months of age. They also mature and die much earlier than we do (which is sad for dog own- ers). Chimps erupt their first molars more on the order of four years of age and do not appear to have natural lifespans that are as long as ours. In other words, rates of dental develop- ment reflect the developmental rates of species, but we would not really know that unless we com- pared humans to other primates. This applies to fossil teeth too: we need a broader comparative context to understand the indica- tions they give us. In your new book, you say that our teeth were adapted for a very dif- ferent diet than the one we eat in Western societies today. Could you explain that briefly? What are the (negative) consequences of this change in diet? Yes. Over most of our evolu- tionary history (until the rise of agriculture around 10,000 years ago), we humans were foragers, eating food that could be gathered or hunted. Those kinds of foods are the foods that our teeth are adapted to eat. With the rise of agriculture, and particularly with the more recent introduction of processed and sugary foods into the diet, there was an enormous in- crease in dental malocclusion and pathology. Essentially, we are not adapted to the diets we eat today, as these dietary changes are quite recent in our evolutionary history. Would you say that today’s dental problems, such as the high pre- valence of dental caries and per- iodontal disease, are man-made evolutional developments? Well, it is possible to find den- tal pathologies in ancient homi- nin fossils, but only in a handful of individuals. So, I would say that, although dental pathologies did occur early in human evolution, they were nowhere nearly as fre- quent as they are today. Why is that? When considering that there were no dentists or even oral hygiene products around, one imagines our ancestors must have been toothless by their mid-20s. With the softer, more cario- genic foods eaten in an agricul- tural diet, the oral bacterial envi- ronment changed. One scientist, Dr Christina Adler, from the Uni- versity of Adelaide and her col- leagues, sequenced bacterial DNA obtained from dental calculus adhering to the teeth of early hunter-gatherer and early Euro- pean agriculturalists. What they found was that, with this change in the oral environment, and later with the production of processed sugar during the Industrial Re- volution, the diversity of oral flora decreased, with caries-causing strains becoming predomi- nant. Essentially, the oral environment had changed to provide an optimal environ- ment for caries-caus- ing strains to flourish. How about primitive tribes that are largely untouched by civilisa- tion even today. Is their dental status significantly better than that of people living in industrial regions? When people who were not eating a Western processed and sugary diet are all of a sudden in- troduced to one, their rates of den- tal disease go up. So, for example, native Eskimos had very little by way of dental caries until they were introduced to processed foods and sugary sodas, and then their rates of caries increased dramati- cally. I have read that breastfeeding provides optimal oral mechanical stimulation for the jaw’s normal development. Given the decrease in breastfeeding, could that mean modern children are at a higher risk of developing malocclusion and re- quiring orthodontic treatment? That is a great question, but as I am not a dental practitioner, I do not have a great answer! I can tell you that Prof. Robert Corruccini’s pioneering experi- mental studies on baboons (which rarely show malocclusions) showed that soft diets led to dental crowd- ing and rotations of teeth. Essen- tially, without foods that were hard or tough, bone growth in the baboon jaw was not great enough to accommodate the animal’s teeth. What role does genetics play in in- fluencing teeth, oral health and jaw development? Since evolution is a process of hundreds and thousands of years, it is probably not possible to turn back the wheel of time just by sticking to a certain diet. Certainly, genetics plays a role. Some individuals are more prone to dental disease than others, but what one eats also plays a role. As far as that goes, there is no per- fect diet, but diets that are low in sugar and eating tough foods that may stimulate jaw growth during childhood might help to alleviate our dental problems. Thank you very much for the inter- view. “The oral environment had changed to provide an optimal environment for caries-causing strains to flourish.” Prof. Debbie Guatelli-Steinberg